1. Field of the Invention
Aspects of the present invention relate to a composition for preparing an electron emitter, an electron emitter prepared using the composition, an electron emission device including the emitter, and a backlight unit including the emitter, and more particularly to an electron emitter that has increased life span, includes a carbon-based material as an electron emission material, and can be easily manufactured; an electron emission device and a backlight unit including the emitter and a composition for preparing the electron emitter used therein.
2. Description of the Related Art
In general, electron emission devices can be classified into electron emission devices using hot cathodes as an electron emitter and electron emission devices using cold cathodes as an electron emitter. Examples of electron emission devices having cold cathodes as an electron emitter include field emission device (FED) type electron emission devices, surface conduction emitter (SCE) type electron emission devices, metal insulator metal (MIM) type electron emission devices, metal insulator semiconductor (MIS) type electron emission devices, ballistic electron surface emitting (BSE) type electron emission devices, etc.
FED type electron emission devices operate based on a principle that a low work function material or high beta function material as an electron emitter easily emits electrons due to an electric charge difference in a vacuum. FED type electron emission devices using a tip-shaped structure mainly formed of Mo, Si, etc., and recently, devices using a nanomaterial such as nanotubes, nanowires, or the like as an electron emitter have been developed.
In an SCE type electron emission device, an electron emitter is formed by disposing a first electrode and a second electrode to face each other on a first substrate wherein a conductive thin film having fine cracks is disposed between the first and second electrodes. As an electric current flows on the surface of the conductive thin film, electrons are emitted from the electron emitter, in areas corresponding to the fine cracks.
MIM type electron emission devices and MIS type electron emission devices include an electron emitter respectively having a metal-dielectric layer-metal (MIM) structure and an electron emitter having a metal-dielectric layer-semiconductor (MIS) structure. The MIM type and MIS type electron emission devices emit electrons using a principle that when a voltage is applied between metals or between a metal and a semiconductor separated by a dielectric layer, electrons are moved, accelerated and emitted from the metal or semiconductor having a higher electron electric charge toward the metal having a lower electron electric charge.
BSE type electron emission devices emit electrons by applying a voltage to an ohmic electrode and a metal thin film, wherein an electron supply layer formed of a metal or semiconductor is formed on the ohmic electrode, and an insulating layer and the thin metal film are formed on the electron supply layer, using a principle that when a semiconductor is miniaturized to a dimension smaller than a mean free path of electrons in the semiconductor, the electrons travel without being dispersed.
The electron emission devices using cold cathodes generally include an electron emission material formed of carbon-based material. To manufacture an electron emitter using the carbon-based material as an electron emission material, a composition for forming an electron emitter including a carbon-based material, a vehicle, insulating material particles; and conductive particles is prepared in a paste form and printed on a substrate.
To properly disperse the materials to a desired degree in the vehicle is difficult as every dispersion degree or dispersive property of each material, which depends on the surface properties of the material, should be considered.